Effective Dielectric Constant of Two Phase Systems

Theoretical approaches to electrical characterization of two phase systems are mostly limited to the systems where the individual components exhibit the same type of conductivity (pure dielectric or pure conductive systems). In this article, the brick wall geometry is extended to the mixed conductive systems with percolation. Impedance spectroscopy techniques were used for experimental investigation of slurries. Various metal oxide powders and host liquids were analyzed using a wide range of solids loadings. Comparison of experimental results with theoretical predictions shows good fitting of the experimental data. Parameters (the values of permittivity for both phases and percolation threshold) calculated from this fitting match the corresponding values of components of two phase systems. Analysis of both low frequency (less than 10 kHz) as well as high frequency (10 kHz to 1 MHz) responses of impedance spectra allows determining of permittivity of dielectric powders suspended in various liquids. Low frequency response provides better accuracy for systems with high dielectric contrast between components, while high frequency response is more accurate for low contrast systems